An accurate assessment of workers"" exposure to the hazardous elements in a workplace is an essential prelude to the task for preventing the occupational illness, protecting the health of workers, and providing a basis for developing and implementing the control measures to minimize the exposure risk. According to the research conducted for years by the U.S. Occupational Safety and Health Research Center, the eight-hour workday time-weighted average exposure levels of workers in a workplace were log-normally distributed, with the exposure variation being substantial large among a group of workers who were subjected to similar exposure. In view of the fact that the production process, the raw materials, and the production facilities of a production plant are seldom changed in a large scale time after time, the exposure variation of workers is mainly due to the workers"" time activity pattern (TAP). However, the accurate TAP data of the workers are technically difficult to gather. In other words, the acquisition of accurate personal TAP data is a technical bottleneck.
As shown in the Reference Material Nos. 1-4, questionnaires, diaries, phone calls, and personal interviews are most widely used to gather the workers"" TAP data. These widely-used tools are by no means reliable in view of the fact that the data so obtained by means of the questionnaires are often not credible due to workers"" lack of recollection of events, workers"" lack of intellectual ability to comprehend fully the questions, workers"" misunderstanding of the questions, or workers"" lack of candidness in answering the questions. In addition, such widely-used tools as described above can not be conveniently executed in the workplace without causing the work interruption on the part of the workers. Aside from the drawbacks described above, these widely-used tools for gathering information of TAP are not cost-effective at best. According to the Reference Material No. 2, a method involving the use of direct observation in conjunction with the real-time recording is the most reliable one for gathering the workers"" personal TAP data; nevertheless it is not economically feasible, not to mention the human factors such as workers"" lack of desire to cooperate, as well as workers"" concern over intrusion of their privacy.
As mentioned in the Reference Material No. 5, a time event recorder (TER) was recently introduced to monitor the workers"" personal TAP. The time event recorder works in such a manner that various operational activities in a workplace are first coded before the time event recorder is given to workers"" who are required to enter manually each operational information into the time event recorder from the onset of the operation. The data are automatically compiled and processed by the TER with precision. As a result, the TER is particularly suitable for use in gathering information on a well-defined event, which takes place with regularity. However, the TER is also subject to error when it is used to gather information on an event which lasts for a short period of time. In light of manual entry of the data by workers, the use of the TER calls for a work interruption on the part of workers, thereby undermining the quality of the process of gathering the data.
As mentioned in the Reference Material No. 6, a ceiling spacing sensor is used to assess the exposure of workers to pollutants in a workplace by monitoring time activities of workers in various locations of the workplace. The sensor is used in conjunction with a transmitter and a receiver, which are help uprightly for measuring the distance between the transmitter and a ceiling. The sensor is portable and can be operated with ease, with the drawback being that the workers"" exposure levels are not directly correlated to the height of ceilings of the workplace. In addition, it is conceivably tiresome for workers to hold the transmitter and the receiver in the upright position. Moreover, the exposure levels may vary greatly from one workplace to another, even if the ceiling heights of different workplaces vary slightly.
In addition to the methods described above, the video technology is also widely used to gather information on exposure, time, activity of workers who are not required to move from one place to another on the floor of a workplace. The video technology is limited in its application because of its limitation in monitoring range and its high cost of equipment, installation and labor. The video technology is not suitable for use in monitoring a variety of exposure sources.
The present invention relates generally to a method for monitoring the exposure time of workers in a workplace, and more particularly to a method for monitoring the exposure time of workers to the harmful chemical substances in the workplace.
The present invention is designed to overcome the deficiencies of the prior art methods described above.
It is the primary objective of the present invention to provide a method for monitoring the personal exposure time of workers in a workplace.
It is another objective of the present invention to provide a method for monitoring the exposure levels of workers at various time blocks.
The method of the present invention involves the use of a sensing device and a recorder to monitor continually the changing conditions of a workplace in a real-time manner, so as to determine the extent to which workers are exposed to a hazardous element existing in the workplace. The workers"" exposure time is monitored continually by means of time clock or watch dog. If necessary, the exposure level of a specific time block can be determined by the method of the present invention.